How to do deployment for php application

I'd start by making the application root of the various servers an SVN working copy. You can add in mod_rewrite (or IIRF ASAPI filters for IIS) rules to ensure people can't address your .svn directories directly.

Then, updating to the latest source can be as simple as an SVN update. For your database update needs, I'd maintain the database modification scripts also in SVN. You'll likely need to wrap the SVN update in a batch/shell script in order to perform the database updates after the scripts are downloaded.

For change management on the live servers, I'd also have their working copies not of trunk, but a release branch. You can merge trunk into the release branch when you are ready for a release. This will allow you to test the deploy and make sure it's solid before performing it on the live servers. It also has the nice side-effect of giving you a nice replica of the site-release versions in case you need to track down issues post-launch.

Lastly, depending on the intensity and timing of these updates, you may also want to have your update script flip an "under maintenance" switch so that users are temporarily met with a proper message rather than a broken site.

Benjamin Eberlei posted a blog a few weeks ago titled Trying a Two Step PEAR/PHAR approach to develop and deploy. He describes is a very interesting and elegant procedure for deploying a PHP application.

I've used subversion as a deployment tool to great effect.

Use svn update on all your production servers, or use phing. (Or use phing to svn update, even.)

Makes rollbacks and backups a snap. Just remember to remove access to any .svn directories.